Hydrostatic bearing type spindle device and machine tool including the hydrostatic bearing type spindle device

Abstract

A hydrostatic bearing spindle device includes: a spindle includes tapered portion having tapered radial receiving surface and flange having first thrust receiving surface and second thrust receiving surface formed at rear side from first thrust receiving surface; first thrust bearing has first thrust bearing surface facing first thrust receiving surface; second thrust bearing has second thrust bearing surface facing second thrust receiving surface; radial bearing facing tapered radial receiving surface; rotation regulator regulates relative rotation of one of first thrust bearing and second thrust bearing with respect to the other; and housing has first screw groove which is screwed with first thrust bearing and second screw groove which is screwed with second thrust bearing. Second screw groove has larger screw pitch than first screw groove does when tapered portion expands rearward, and first screw groove has larger screw pitch than second screw groove does when tapered portion expands frontward.

What is claimed is: 
     
       1. A hydrostatic bearing type spindle device to which a tool or a workpiece is detachably fixed, the hydrostatic bearing type spindle device comprising:
 a spindle that is configured to have a front end to which the tool or the workpiece is detachably fixed and that comprises a tapered portion having a tapered radial receiving surface and a flange having a first thrust receiving surface and a second thrust receiving surface formed at a rear side from the first thrust receiving surface; 
 a spindle rotation driving device that rotates the spindle; 
 a first thrust bearing that has a first thrust bearing surface facing the first thrust receiving surface in parallel with a first gap formed therebetween and that is penetrated by the spindle; 
 a second thrust bearing that has a second thrust bearing surface facing the second thrust receiving surface in parallel with a second gap formed therebetween and that is penetrated by the spindle; 
 a radial bearing that has a tapered radial bearing surface facing the tapered radial receiving surface in parallel with a third gap formed therebetween and that is penetrated by the spindle; 
 a rotation regulator that allows one of the first thrust bearing and the second thrust bearing to relatively move with respect to the other in an axial direction but regulates relative rotation of one with respect to the other; and 
 a housing which has a first screw groove screwed with the first thrust bearing and a second screw groove screwed with the second thrust bearing and accommodates the spindle, the first thrust bearing, the second thrust bearing, and the radial bearing and to which the radial bearing is fixed, 
 wherein the second screw groove has a larger screw pitch than the first screw groove does when the tapered portion expands rearward, and the first screw groove has a larger screw pitch than the second screw groove does when the tapered portion expands frontward. 
 
     
     
       2. The hydrostatic bearing type spindle device according to  claim 1 ,
 wherein the rotation regulator has a key member which is fixed to the second thrust bearing and extends in a radial direction and a guide groove which is formed in the first thrust bearing and guides the key member in parallel with an axis of the spindle. 
 
     
     
       3. The hydrostatic bearing type spindle device according to  claim 1 , wherein
 two or more tapered portions are formed on an outer circumference of the spindle, and 
 the hydrostatic bearing spindle device includes two or more radial bearings. 
 
     
     
       4. The hydrostatic bearing type spindle device according to  claim 1 ,
 wherein a taper ratio of the tapered portion is 1/50 to 1/10. 
 
     
     
       5. The hydrostatic bearing type spindle device according to  claim 1 , further comprising
 a thrust bearing rotation driving device that rotates at least one of the first thrust bearing or the second thrust bearing. 
 
     
     
       6. The hydrostatic bearing type spindle device according to  claim 5 , further comprising
 a control device that controls the thrust bearing rotation driving device. 
 
     
     
       7. The hydrostatic bearing type spindle device according to  claim 1 ,
 wherein the first gap, the second gap, and the third gap have the same size. 
 
     
     
       8. The hydrostatic bearing type spindle device according to  claim 1 , further comprising
 a fluid supply device that supplies a fluid to each of the first gap, the second gap, and the third gap. 
 
     
     
       9. The hydrostatic bearing type spindle device according to  claim 8 , wherein
 the housing has a first fluid supply port, a second fluid supply port, and a third fluid supply port, 
 the first thrust bearing has a first fluid outlet formed in the first thrust bearing surface and first fluid supply piping through which the first fluid outlet and the first fluid supply port are connected to each other, 
 the second thrust bearing has a second fluid outlet formed in the second thrust bearing surface and second fluid supply piping through which the second fluid outlet and the second fluid supply port are connected to each other, 
 the radial bearing has a third fluid outlet formed in the tapered radial bearing surface and third fluid supply piping through which the third fluid outlet and the third fluid supply port are connected to each other, and 
 the fluid supply device is connected to each of the first fluid supply port, the second fluid supply port, and the third fluid supply port. 
 
     
     
       10. A machine tool comprising the hydrostatic bearing type spindle device according to  claim 1 .